The goal of this research proposal is to examine the neuroendocrine regulation of selective FSH release in the female rat. A push-pull in vivo perfusion system will be employed to determine if selective FSH release occurs as a result of changes (i.e., magnitude, frequency) in hypothalamic luteinizing hormone-releasing hormone (LHRH) release. If no changes in LHRH release are observed, animals will be given an LHRH antagonist to ascertain whether tonic LHRH release is essential for selective FSH release to occur. Further experiments will be conducted to eliminate all hypothalamic input to the anterior pituitary gland by lesioning the median eminence or transplanting the pituitary gland under the kidney capsule. As well, basal FSH secretion and pituitary responsiveness to LHRH will be assessed in vitro in order to determine if increases in these parameters precede or occur during instances of selective FSH release. The results of these studies should provide important information which severely questions the physiological necessity for a separate FSHRH distinct from LHRH. Indeed, the results may suggest that the pituitary selectively releases FSH independent of any hypothalamic input. With regards to basic research, it is anticipated that the data gathered from these experiments could provide the impetus to examine how the pituitary gonadotroph selectively releases FSH on a molecular level since this cell presumably contains both LH and FSH. From a clinical standpoint, the relevance of these studies is enormous since many reproductive disorders such as luteal phase defects are attributed to abnormal ovarian function as a consequence of inappropriate FSH secretion during the follicular phase. Therefore, knowledge concerning the regulation of FSH secretion should aid the clinician in effectively treating these types of disorders.